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MASWE-0024: Improper Use of Message Authentication Code (MAC)

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Initial Description or Hints

Improper use of MACs in security sensitive contexts affecting data integrity.

Relevant Topics

  • Using HMAC with keys with insufficient entropy
  • Using HMAC with missing timestamp (or nonce)
  • Using MAC‑then‑encrypt or encrypt‑then‑MAC incorrectly, leaking information via timing or error messages
  • Allowing predictors (users or attackers) to control data inputs, creating scenarios where forged or replayed tags bypass integrity checks.
  • Hash functions lacking collision resistance (e.g., MD5 or SHA‑1 used in HMAC)
  • Use of non‑cryptographic checksums (e.g., CRC‑32 instead of HMAC)
  • MAC constructions that fail outside narrow assumptions (e.g., raw CBC‑MAC on variable‑length messages)
  • Tags that are too short significantly lower the effort required for forgery

References

MASTG v1 Coverage